Gardening
in Tucson, Phoenix,
and Southern California

Gardening in Tucson, Phoenix, and Southern California

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Olneya tesota: Desert Ironwood

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Description
Form: Single to multi-stemmed shrub, or with pruning, tree.
Leaf retention: Evergreen except will drop leaves under three conditions: before blooming (only in some years), extreme drought, and cold temperatures below its hardiness range.
Growth rate: Slow. Supplemental water speeds growth.
Mature Size: 15-30' high and 15-25' wide.
Flowers: Pea-flower shaped, light purple wing petals with other petals being white or pink, clustered on short shoots that grow from the middle of stems.
Bloom: In spring after leaves have dropped, but blooms less than half of all years in total.
Fruit: Hairy, brown seed pod. Seeds are edible only after roasting.
Leaves: Tiny, oval, thick, bluish gray-green, paired leaflets. Each compound leaf has pair of thorns at base. Provides medium shade.
Stems: Thorny. Wood is dense, heavy, sinks in water, and contains chemicals toxic to wood-rotting microbes.
Roots: Nitrogen-fixing*.
Wildlife: Attracts bees, birds, browsed by large mammals. Provides shade to smaller plants and many animals in the desert.
Toxic / Danger: Thorns. Dust from wood cutting is possible breathing hazard.
Origin: California, Arizona, Mexico.

Cultivation and Uses
USDA hardiness zones: 9-11. Young trees hardy to 25°F, older ones to 20°F.
Heat tolerant: Yes.
Drought tolerant: Yes.
Sun: Full sun.
Water after becoming established: Once every month or two during drought.
Soil: Well drained, dry, low in organic content, pH 6.6-8.5 (neutral to alkaline). *Do not use a nitrogen fertilizer.
Prune: To shape and thin.
Litter: Leaf drop; prevented by monthly watering during drought.
Propagation: Seed.
Uses: Ornamental, shade, xeric garden.

Comments
This plant is a protected species. Very long lived — some specimens are centuries old. A few commercial varieties are selected for improved cold hardiness.



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